A steering system for a working vehicle, which is already equipped in an actual machine, comprises front and rear wheels, a steering apparatus for steering the front and rear wheels, mode changing means for changing over a mode of steering the front and rear wheels among two-wheel steering (2WS), opposite-phase four-wheel steering (4WS) and in-phase four-wheel steering (Crab), and mode instructing means for instructing change of the mode of steering the front and rear wheels.
The mode instructing means is constituted as a dial-type mode change switch having three shift positions “4WS”, “2WS” and “Crab”. These three shift positions are visually labeled as “4WS”, “2WS” and “Crab”. Also, as soon as the mode change switch is shifted, a mode changing valve serving as the mode changing means is also shifted to make the selected mode effective. A neutral lamp is provided which is turned on when the front and rear wheels are at neutral. When changing the steering mode, an operator shifts the mode change switch after confirming that the neutral lamp is turned on.
EP0300774A2 and EP0439370A1 propose a system in which, even when the mode change switch is shifted, the mode changing valve is kept from shifting until the front wheels come into neutral, and the mode changing valve is shifted and the selected mode is made effective only after the front wheels have come into neutral.